Vulnerability · Published Aug 27, 2026 · Assigned by GitHub_M
CVE-2026-77341cpp-httplib: CRLF injection via unvalidated HTTP trailer headers in chunked response writing
Medium 5.3
In plain English
A medium-severity security flaw in cpp-httplib from yhirose. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 40% of all known vulnerabilities).
Official description
cpp-httplib is a C++ header-only HTTP/HTTPS library. In version 0.49.0, the chunked-response trailer output path writes trailer header names and values directly to the socket without validating them, allowing CRLF sequences in a trailer field to inject additional headers or split the HTTP response. Unlike every other header-writing path in the library, the trailer-writing code applies none of the field-name and field-value checks that reject carriage return and line feed, so an application that places attacker-influenced data into a chunked response trailer emits attacker-controlled CRLF onto the wire. This enables HTTP response splitting, letting an attacker forge response headers or inject a second response. This issue is fixed in version 0.50.0.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | cpp-httplib | no fix listed | DEBIAN-CVE-2026-77341 |
| Debian:13 | cpp-httplib | no fix listed | DEBIAN-CVE-2026-77341 |
| Debian:14 | cpp-httplib | no fix listed | DEBIAN-CVE-2026-77341 |
| Ubuntu:26.10 | cpp-httplib | no fix listed | UBUNTU-CVE-2026-77341 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| yhirose | cpp-httplib | >= 0.49.0, < 0.50.0 |
Weakness: CWE-93, CWE-113 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N